Here's why:
* Metaphor: A metaphor directly compares two unlike things without using words like "like" or "as." In this case, the concert is being compared to a river, and the "endless valley" is a metaphor for the audience or the space the concert is filling.
Let's break down why it isn't other types of figurative language:
* Simile: A simile uses "like" or "as" to make a comparison. For example, "The concert was *like* a river snaking through an endless valley."
* Personification: Personification gives human qualities to inanimate objects or animals. There is no personification in the example line.
* Hyperbole: Hyperbole is an exaggeration. While the idea of a concert as "endless" could be considered hyperbole, the overall sentence is not an exaggerated statement.
* Alliteration: Alliteration is the repetition of consonant sounds. The example line doesn't have a strong pattern of alliteration.
Let me know if you'd like to explore more figurative language examples!